1. Field of the Invention
This invention relates to processes for producing 3-cyanopropanol from 3-cyanopropanal. In a further aspect, the invention relates to processes for preparing 3-cyanopropanol comprising reacting 3-cyanopropanal with hydrogen in the presence of an especially prereduced copper-chromite catalyst. In a still further aspect the invention relates to processes for preparing 2-pyrrolidone comprising the step of reacting 3-cyanopropanal with hydrogen in the presence of the prereduced copper-chromite catalyst.
2. The Prior Art
3-cyanopropanol is an intermediate for the preparation of gamma-butyrolactone, a commercial solvent, and 2-pyrrolidone. 2-pyrrolidone can itself be used as a solvent or can be used as an intermediate for other commercial solvents. More importantly, however, 2-pyrrolidone can be homopolymerized to poly-2-pyrrolidone, commonly known as nylon-4. For example, one suitable polymerization process is described in U.S. Pat. No. 3,721,652.
Poly-2-pyrrolidone can be molded into fibers, films, and other shaped articles. Poly-2-pyrrolidone's advantages as a textile fiber having good water-retention properties are particularly notable.
In the preparation of poly-2-pyrrolidone it is very important to use very pure 2-pyrrolidone monomer, because the polymerization is very sensitive to impurities. Since the presence of certain impurities or by-products formed in the preparation of 2-pyrrolidone can inhibit the polymerization reaction or can, in fact, adversely accelerate the polymerization reaction, causing a poor-quality, low-molecular-weight polymer product to be produced. Thus, it is very important to prepare 2-pyrrolidone from high-purity intermediates to ensure than high-pyrity 2-pyrrolidone is obtained.
Accordingly, in one aspect, the present invention is concerned with an improved process for producing high yields of very high-quality 3-cyanopropanol reaction product mixture which can be used to prepare very pure 2-pyrrolidone.
The preparation of 3-cyanopropanol by the hydrogenation of 3-cyanopropanal is known and is disclosed in Kogyo Kagaku Zasshi, Vol. 74 (9), 1830-1834 (1971), using a cobalt carbonyl catalyst and in U.S. Pat. No. 3,141,895 using palladium-carbon, platinum-carbon, nickel or copper-chromium catalyst. The Kogyo publication also teaches that 3-cyanopropanol can be converted to pyrrolidone by heating with aqueous ammonia.
W. R. Ness teaches in the Journal of Organic Chemistry Vol. 23, pages 899 and 900 (1958) that boiling copper-chromium oxide in cyclohexanol increases the ability of this catalyst to hydrogenate acetone to 2-propanol at lower temperatures and to oxidize certain steroid alcohols to the corresponding ketones at lower temperatures. The JOC publication also teaches that during the activation treatment, the cyclohexanol is simultaneously oxidized to cyclohexanone.
It has now been discovered that with respect to the catalyzed reaction of 2-cyanopropanal with hydrogen that by treating a copper-chromite catalyst with hydrogen or an alkanol or cycloalkanol at elevated temperatures that not only is the activity of the catalyst increased, but surprisingly the selectivity of the catalyst for 2-cyanopropanol, and gamma-butyrolactone is greatly increased. The combination of increased activity (i.e., conversion) and increased selectivity is particularly surprising and affords a large compounded increase in the yields of the desired products, which can be readily converted to 2-pyrrolidone in high yields via treatment with ammonia.